FAK is a protein tyrosine kinase (PTK) that localizes to focal adhesions and is regulated by cell surface receptors called integrins. The ability of FAK to localize to focal adhesions is essential for its regulation and for transmission of downstream signals. FAK functions in regulating cell motility and transmits an adhesion-dependent cell survival signal. FAK may be involved in human cancer since: i) it was isolated as a Src associated substrate and activated Src has been described in human tumors. ii) changes in expression of integrins have dramatic effects upon the malignant phenotypes of cancer cells, and iii) FAK is overexpressed in some human tumors. Thus the analysis of basic FAK function and establishment of model systems of FAK overexpression may yield valuable information about the development of cancer. The current project has four main objectives: 1) to identify the binding partners that target FAK to focal adhesions. A microinjection strategy will be applied to test the role of known FAK binding partners to function in targeting. In addition, talin-/- cells will be utilized to address the role of talin in FAK targeting. Strategies to isolate novel binding partners are presented. 2) Breast epithelial cell models will be used to test the role of FAK in the acquisition of cancerous phenotypes. Wild type and activated FAK will be expressed in the MCF-10A and HCII normal breast epithelial cell lines and the phenotypes observed to determine if any parameters of oncogenic transformation have been acquired. The dominant negative FAK variant, FRNK, has been expressed in the T47D breast cancer cell line. This system will be used to assess the role of FAK in maintaining the cancerous phenotypes of these cells. 3) The crosstalk between integrin/FAK signaling pathways and growth factor receptor signaling pathways, specifically the EGF receptor family, in breast epithelial cells will be examined. Since the signaling via the EGF receptor family of PTKs is strongly linked to breast cancer the interplay between FAK and these signaling pathways may be highly significant in the pathogenesis of breast cancer. 4) Finally, a transgenic mouse model of FAK overexpression in the epithelium of the mammary gland will be established to assess its role in the development of mammary tumors in vivo. Expression of wild type and activated FAK will be targeted to mammary gland using the MMTV promoter. Mice will be examined for normal gland development and the formation and metastasis of mammary gland tumors. Genetic interactions between FAK and the Src and Neu oncogenes in the development of mammary tumors will also be examined.